Regular exercise and good nutrition are both important for personal health. A healthy lifestyle requires the balance between calorie loss (e.g. through exercise) and calorie intake (e.g. through food or drink). A person who wants to lose weight needs to burn more calories than their intake, whereas a person who wants to gain weight needs to take in more calories than their loss.
An activity tracker is a device or application for monitoring and tracking fitness-related metrics such as distance walked or run, calories burned, and in some cases blood sugar levels, heart-beat and quality of sleep. The term is now primarily used for dedicated electronic monitoring devices that are synchronized, in many cases wirelessly, to a computer or smartphone for long-term data tracking, an example of wearable technology.
An activity tracker typically includes one or more sensors that can measure the movement and/or some physiological parameters (e.g. heart rate, etc.) of the user. Based on the measurement data, calculations can be made to estimate the calories burned by the user. These measurement data and the calculated calories burned can be stored in the device and/or the accompanying computing device (e.g. smartphone), for data logging and trending.
While many activity trackers have proprietary algorithms to estimate the calories burned, most of them do not have a convenient way to monitor user's calorie intake. Typically, to track a user's calorie intake, the user must maintain a diary by manually entering his/her food or drink consumption through a computing device (e.g. smartphone). This user input function is typically implemented through a hand interacting interface of the computing device, e.g. the keyboard, keypad, touch screen, etc. However, this method of manual input is inconvenient for the user, as it distracts the user from other activities by shifting attention to the hand interface of the computing device in order to enter the information. Consequently, many users are reluctant or not consistent to use such features to track their calorie intake and therefore discouraged from using these trackers at all.
Another problem associated with most activity trackers is that the tracker only provides information about the estimated amount of calories burned due to activities, without giving more concrete instructions to the user on what actions the user should take in order to achieve his or her personal goal. For example, the activity tracker may notify the user that 1000 calories were burned for the day, but what the user should do next in order to achieve his or her personal goal with regards to calorie intake or loss is left unknown to the user.
Yet another challenge for all existing activity trackers, is that the formulas for estimation of calorie intake and loss are static. In other words, once the corresponding software application (app) is installed in the computing device, the formulas and the associated parameters for estimating user's calorie intake and/or loss are fixed. However, it is known that different people have different physiological profiles, thus their metabolic rates also differ. Even the same person's metabolic rate can change over time. Therefore, a fixed formula for calorie estimation cannot account for such inter- and intra-subject variabilities. Furthermore, many activities that burn calories cannot be measured by the activity tracker, such as physical activities involving isometric exercise and most types of mental work (e.g. reading, thinking, etc.), thus the associated calories burned cannot be accounted for.